Worried about sharks? Blame Spielberg, not science

Massachusetts marine biologists have good news for residents hitting the beach this summer: Chances are you won't end up as shark bait.

ARIEL WITTENBERG

Massachusetts marine biologists have good news for residents hitting the beach this summer: Chances are you won't end up as shark bait.

Last summer was filled with shark sightings, beginning with the frightening photograph that went viral online of a shark in pursuit of an Orleans kayaker and ending in September when a 13-foot great white shark washed ashore in Westport.

Between those two events and a great white biting a swimmer in Truro, all fingers pointed to an overabundant seal population allegedly drawing more great whites to Massachusetts waters.

But shark and seal experts say humans are not likely to find themselves in a new Steven Spielberg "Jaws" sequel any time soon. So far, at least, there's no proof that Massachusetts' shark population is increasing along with seals. More comforting, perhaps, is that experts say sharks "don't like eating people."

"A lot of people think sharks are the garbage disposals of the sea," said Division of Marine Fisheries shark expert John Chisholm. "But they are very intelligent and they know what they want to eat. That's not humans."

Harbor and gray seals used to be plentiful along the East Coast until 1888, when Massachusetts began a 74-year-long seal bounty program. Motivated by angry fishermen who thought the pinnipeds were stealing their catch, the state paid poachers for each seal nose or tail they brought in. It's estimated that between 72,000 and 136,000 seals were killed between 1888 and 1962 for bounties.

In 1962 Massachusetts stopped the bounty program, and 10 years later the Marine Mammal Protection Act of 1972 provided the animals with a federal safety net.

Since then, the seal population has been steadily increasing in a "classic victory for the ecosystem," according to C.T. Harry, who works as a Cape Cod-based coordinator of marine mammal research for the International Fund for Animal Welfare.

Seal stock assessments by NOAA have the population of gray seals rising from roughly 2,000 in waters around Maine and Massachusetts in 1994 to more than 15,000 in just Massachusetts in 2011. But, Harry said, there is still much to learn about the seal population.

"We are still learning about how they move and where they go," he said, adding that there is no way to guarantee that the seals are not double-counted as they migrate.

While the increase in New England seal counts may seem large, NOAA scientist Jason Link called it "healthy population growth" and noted that Canadian seal populations have boomed at much higher rates.

Seals eat a variety of prey, focusing at times on small groundfish like juvenile cod. They like to congregate in places where there are long sandbars and beaches to laze in the sun.

In Massachusetts, they are commonly found near Chatham and Muskeget Island off of Nantucket.

As the climate changes, seals' homes change, too. Harry said his group has found new seal gathering places in recent years in Truro and sometimes Barnstable as new sandbars are created.

There are no known seal colonies in Buzzards Bay, where the shore is more rugged and rocky than on the Cape. But, Harry said, if the ecosystem and food sources change, seals will adapt and "change their range."

"They are moving into areas where we previously haven't seen them before," he said. His organization has seen a "slight increase" of seal reports in Buzzards Bay from Marion down to the Massachusetts-Rhode Island board. But the sightings are rare.

"Their real migratory corridor is from Nantucket up north to Canada," Harry said.

Though the seal population is increasing and perhaps changing location, Link said it is unlikely to have a profound effect on the Massachusetts marine ecosystem.

"Seals have always lived here," he said. "Maybe not in these numbers, but the system knows how to handle them. They are not an invasive species."

He said seal population increases are too recent and not well-studied enough to know what the impact may be.

"It's like if you have a bowl of Jello and you knock it, you know it will wiggle, but you can't predict how it will behave exactly," he said.

One common hypothesis is that an increase in seal populations could in turn increase the number of their predators, like great white sharks. But, Link said, "That's just a hypothesis. There is no smoking gun."

Like seals, great white sharks have always existed in Massachusetts waters, including when the seals were near-extinction, according to Chisholm of DMF.

There is no historic population data on great white sharks, something Chisholm and the DMF are trying to fix by catching, tagging and releasing great whites. But, Chisholm said there is no evidence to indicate the North Atlantic population has been growing in recent years.

In fact, he said, most sightings of great whites indicate the fish are older because of their size.

"Great whites are very slow growing," he said. "When you see videos of huge sharks feeding on seals off of Chatham, those sharks have been around a while."

That's not uncommon in the animal kingdom, with wolf and lion populations often being vastly outnumbered by their prey, Chisholm said.

The number of shark sightings close to land has been increasing. It used to be only a few per year, Chisholm said, but "in recent years we're having more like a dozen confirmed sightings."

That could be because the sharks are moving closer to shore as they find more seals, in places like Chatham and Naushon Island.

"They aren't following or stalking the seals, they are finding them," Chisholm said. "Then they remember where they got their last meal."

Harry said the increase in shark sightings could be because more people are looking for them, not because they are moving closer to shore.

Sharks eat seals where they find them, but do not follow them, Link said. That means an absence of seals in SouthCoast does not necessarily translate to an absence of great whites.

But, not all reported great white sharks turn out to be great whites. The Orleans kayaker, whose video went viral last summer, was most likely being chased by a basking shark, a very large breed of fish that swims quickly through the water "filter feeding" with its mouth open.

Those sharks are often mistaken for great whites due to their size, but Chisholm says there are distinct physical differences, the most notable being that basking sharks are toothless.

"They have rough skin, so if you touch them it could certainly do some damage, but they aren't going to chomp anything," Chisholm said.

Link blamed American culture and the movie "Jaws" for hysteria surrounding great white sharks.

"The scenes in that film are pretty nasty," he said. "But there are other animals in the ocean that are nasty that you never hear about."

While Chisholm says the great white's main prey are seals, he admits that humans do sometimes find themselves being pursued by the animals in cases of "mistaken identity."

"We look very similar to seals in body type, shape and form," he said. That includes free-swimming people and those using small recreational crafts like surfboards and kayaks.

Usually when great whites go after people, Chisholm said, it's not a "fully-committed predatory event" but merely an "investigatory bite" to check and see if they are, in fact, seals. That means that a shark won't use the full force of its massive jaws to incapacitate its target, but just taking a moment to "hold it in its mouth to see if it's worth eating."

"A shark's job is to look for prey. If a great white sees something that looks like prey, the only way to know if it's edible or not is to taste it," he said. "They don't have fingers to poke you so their only option is their teeth."

According to Chisholm, a great white will know after one bite if it's eating a human and leave it alone the same way humans "know the difference between a fork and what's on the fork."

Additionally, "investigations" usually go after a prey's limbs and not torsos, meaning they often do not hit vital organs. Indeed, the last fatal great white attack in Massachusetts was in Mattapoisett Harbor in 1936. According to The Standard-Times archives, that victim was bitten on his left leg and died from loss of blood before surgeons could finish treating him.

Since then, Chisholm notes, emergency medical services have improved. So while such "investigations" can cause lasting damage, they aren't likely to be fatal.

"We're nothing but flesh and blood and they have a mouth full of steak knives, so it's understandable that people have overwhelming fears of shark attacks," he said. "But if great whites were actually man eaters, we'd have a lot more attacks on humans and more would be fatal."

Though some have suggested culling the seal population would help reduce shark attacks, Chisholm called that idea "ridiculous."

"It won't chase the sharks away, they will just find other food," he said.

Harry agreed, noting that places without seal populations still have thriving great white shark populations, such as Florida.

"Drawing out that correlation is dangerous and not something that is scientifically proven or effective," he said.

He noted that while the incidence of sharks attacking humans is rare, beachgoers need to be aware that when they swim in the ocean they are newcomers to an established ecosystem.

"People need to understand that if you swim in the ocean you could be subjecting yourself to the whims of whatever lives in the ocean," he said. "You need to accept that you're entering creatures' habitat and not try to change it."

Avoiding sharks does not mean avoiding the water entirely, just using "common sense," Chisholm said.

"Don't swim where you see seals," he said.

But, he said, at the end of the day, most beachgoers will be perfectly safe taking a dip. "You're probably in more danger of injury driving to the beach than from swimming once you get there," Chisholm said.